Question

Myoglobin stores oxygen for metabolic processes in muscles. Chemical analysis shows that it contains 0.35% Fe by mass. If there is one Fe atom and 6 N atoms per molecule of myoglobin, which of the following option is not correct about myoglobin?
(Molar Mass of Fe = 56 g/mol)

• A. Molar mass of myoglobin is 16000 g/mol
• B. One molecule of myoglobin contains 84 gm nitrogen atoms.
• C. % content of nitrogen in myoglobin is 0.525%
• D. If one molecule of myoglobin can absorb one molecule of oxygen gas then after absorption of oxygen there will 0.2% increase in mass.

Answer 1

The correct option is B One molecule of myoglobin contains 84 gm nitrogen atoms.

Let, molar mass of myoglobin be $x$. As $x$ contains 0.35% of Fe.
So, $x\times \frac{0.35}{100}=56$
$x=\frac{56\times 100}{0.35}=16000g/mol$
(a) Molar mass of Myoglobin is 16000 $g/mol$
(b) As one molecule of myoglobin contains 6 nitrogen i.e. 84 amu nitrogen atom.
(c) Fraction of nitrogen atoms present is given by $=\frac{84\times 100}{16000}=0.525\%$
(d) When one molecule of myoglobin absorbs one $O_2(molarmass=32g/mol)$
% increase of oxygen $=\frac{32\times 100}{16000}=0.2\%$